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KT88, vs KT120 vs KT150

I received an interesting question today about using the new Tung-Sol KT150 in our KT88 designed amps. Besides being arguably one of the ugliest looking new tubes I've seen in quite a while, this tube does specify a pretty heft filament current.

Out of curiosity, I contacted the manufacturer and they confirm that the KT150 typically pulls 1.75A, for a quartet total of 7A, or an increased load of about 9% over a typical KT88 (6.4A) . That shouldn't present a problem, but it's nice to know what the actual outcome will be.

Here's why:

A high filament voltage will make the tube sound brighter than a low one, so if the KT150 causes the 6.3 volt supply to drop 9% (5.78V), you might conclude that the KT150 is "softer sounding" than the stock KT88. The only way to know for sure how the KT150 really behaves compared to the KT88 is to run them under identical conditions. Since that's not something the end user can do, your conclusion is going to be based an amalgam of circumstances beyond your ability to compensate for.

Because our power transformers are of a robust design, a full 9% voltage drop is probably unlikely, but we'll never know until we measure it.

So, if you're buying the Tung-Sols for any reason other than that they remind you of the thingie you used in prison to store your valuables, it's probably worth looking into their affect on the filament voltage supply.

I'll update this thread as soon as we receive a sample set for testing.

The fact that Stephen appears from nowhere, is sentenced to death in an emotional public trial without anyone interfering at all and is then altogether forgotten as if nothing happened, is already suspicious.